It was a triumphant return for the band, which last performed on New Year’s Eve at the same venue in 2003, and took a much-needed break shortly afterward following two decades of relentless recording and touring. The joyous roar that greeted Phish — lead singer/guitarist Trey Anastasio, keyboardist Page McConnell, bassist Mike Gordon and drummer Jon Fishman (clad as usual in a house-dress covered with “Phish circles”) — showed just how much the group was missed.